GPS World, February 2012

THE SYSTEM Increase Proposed for GLONASS A December 27 meeting in Moscow heard a proposal to expand the GLONASS constellation to 30 satellites and six orbital planes among five other modernization options The Presidium of the TsNIImash Council Central Research Institute of Machine Building is the arm of Roscosmos the Russian federal space agency responsible for civil aspects of GLONASS The other options include adding one more satellite to each of the existing three planes but that would involve rephasing almost all of the operating satellites which could cause problems Adding three new planes to the constellation each with two satellites is the leading option and will be considered in detail over the next few months It is not clear how the present GLONASS frequency division multipleaccess FDMA channel spectrum could handle 30 satellites It appears that the current arrangement can only handle a maximum of 28 satellites The concept would need support from the Russian Defense Ministry among others to go ahead Incomplete Compass ICD Released China announced the official start of Compass operational positioning navigation and timing services to China and surrounding areas and released a test version of an interface control document ICD on December 27 The ICD is available in both Chinese and English in PDF format from the systems website www beidou gov cn The nine page test ICD is incomplete It only describes the basics of the coordinate and time systems and the basic characteristics of the open service B1 signal transmitted as the in phase component on the 1561098 MHz carrier frequency including the ranging codes assigned to different satellites There is no discussion of the details of the navigation message or associated algorithms A spokesperson stated that the test version is being released to stimulate research and development work and promote applications as soon as possible and that some aspects of the transmitted signals are not yet finalized or cured and that is why they are not discussed in the test ICD Leap Second The International Earth Rotation and Reference Systems Service IERS announced that a positive leap second will be introduced into Coordinated Universal Time UTC at the end of June 2012 UTC will be retarded by 10 second so that the sequence of dates of the UTC markers will be 2012 June 30 23h 59m 59s 2012 June 30 23h 59m 60s 2012 July 01 0h 0m 0s UTC and all time scales based on UTC will be affected by this adjustment However GPS will not be adjusted physically For GPS the leap second correction contained within the UTC data of subframe 4 page 18 of the navigation message transmitted by satellites will change Before the leap second GPS UTC 15s that is GPS is ahead of UTC by fifteen seconds After the leap second GPS UTC 16s GPS will be ahead by sixteen seconds Meanwhile the International Telecommunication Union postponed until 2015 a vote on a proposal to do away with leap seconds completely OUR VISION FOR GPS ANY POWER ANY FREQUENCY ANY DENSITY ANYWHERE www locatacorp com YOUR OWN GPS The Local Constellation is launched ION 2011 The trademarks Locata GPS 20 Your Own GPS and Local Constellation are registered to Locata Corporation www gpsworld com February 2012 GPS World 11